Factors affecting dissolved phosphorus and nitrate concentrations in ground and surface water for a valley dairy farm in the northeastern United States

Agriculture often is considered to be a contributor of soluble reactive phosphorus (SRP) and nitrate-N (NO₃-N) to surface waters. This research analyzed SRP and NO₃-N concentrations in groundwater and in a creek fed by groundwater on a valley dairy farm in the Cannonsville basin of the New York City watershed.

Water-table depth and concentrations of SRP, NO₃-N, dissolved organic carbon (DOC), and dissolved oxygen were measured at regular intervals over a three-year period. A multivariate mixed model analysis of variance indicated that the SRP and NO₃-N concentrations were controlled primarily by environmental variables, including precipitation and water table depth; source variables, including manure applied and crop type; and chemical variables, including DOC and dissolved oxygen concentrations in groundwater.

The highest groundwater concentrations of NO₃-N and SRP were found at the shallowest water-table depths, which has implications for agricultural nutrient management in areas with shallow groundwater.

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